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N5 Biology Cell Biology subunit 3 DNA and Making New Cells Making New Cells simple cell division diagram membrane nucleus nucleus membrane nucleus nucleus nucleus Species human chromosome Number of complement matching pairs 46 fruit fly 8 4 snail 54 27 cabbage 18 9 23 Duplicated chromosome centomere chromatids Stages of Mitosis Click here for mitosis animation http://www.cellsalive.com/mitosis.htm More Mitosis Animations Click here for Time lapse film of mitosis (1.30 mins) http://www.bbc.co.uk/learningzone/clips/cell-division-bymitosis/4189.html Click here for you Tube video (10 mins) http://www.youtube.com/watch?feature=player_emb edded&v=L0k-enzoeOM#! Stages of Mitosis text from pupil booklet When the chromosomes become visible they appear as double threads called chromatids joined by a centromere. Structures in the cell called centrioles migrate to opposite ends of the cell - the ‘north and south poles’. The membrane round the nucleus disintegrates and the chromosomes line up along the equator – in between the north and south poles. Spindle fibres from the centrioles attach to the centromere of each chromosome. The spindle fibres shorten and pull the chromatids apart. One chromatid from each pair moves to the north pole and the other one moves to the south pole. Two new nuclei form when the nuclear membrane forms round each set of chromatids – now called chromosomes. The cell then divides in two Looking at Dividing Cells You may see some cells under the microscope like some of the cells below Looking at Dividing Cells Cell production Click here for film showing how new skin cells are grown (3.09 mins) http://www.bbc.co.uk/learningzone/clips/growing-new-skin-cells/111.html Click here to see a Youtube film of AsepticTechniques while transferring culture medium from a bottle to an agar plate (only watch from start to 6 mins) http://www.youtube.com/watch?v=gQvZ4opDcno&feature=player_embedde d Aseptic Technique technique heat glassware in an autoclave (pressure cooker) to 121oC wash hands before and after experiment hold lid over open petri dish reason sterilise equipment remove microorganisms from skin prevent entry of unwanted microbes flame innoculating loop destroy unwanted microbes on wire lids held onto inoculated petri dishes with tape prevent entry OR exit of microbes from agar surfaces disinfected before and after experiment kill microbes on work area DNA and Genes • A gene determines an organisms characteristics. • Genes are found on chromosomes . • Chromosomes are found in the nuclei of all cells. • Chromosomes are threadlike structures made from DNA . DNA nuclei chromosomes gene DNA Structure weak hydrogen bond deoxyribose sugar phosphate base nucleotide strong chemical bond double stranded DNA Click here for website with template and instructions for origami DNA model http://www.dnai.org/teacherguide/guide.html Finished product should look like this DNA discovery Click here for Youtube video http://www.youtube.com/watch?v=7yE3Z5f7i0&feature=player_embedded#! DNA: The secret of life, a programme about the race to uncover the structure of DNA. Contains interviews from the scientists involved in the discovery (53mins) Click here for DNA Timeline Activity http://www.dnai.org/teacherguide/guide.html